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Crown Gall and Cane Gall

Crown and cane gall are bacterial diseases that seriously limit raspberry
production in Pennsylvania. Crown gall is the more widespread of the two
diseases and affects all brambles as well as apples, grapes, peaches, and roses.
Only grass-like plants seem to be immune to crown gall. Cane gall occurs only on
brambles, with black and purple raspberries being more frequently infected than
red raspberries and blackberries. The impact of the disease on plant growth and
production can range from no apparent effect to the death of the plant.

Symptoms Crown and cane gall are characterized by the
spongy, rough, pinhead- to golf ball-sized, tumor-like swellings that become
brown, woody knots with age. Crown galls develop in the spring on the
underground parts--the roots and crown--of the plants. Cane galls develop as
whitish eruptions on the fruiting canes in mid-June. These eruptions later turn
brown and then black and begin to disintegrate. More intense gall formation
seems to occur in years with higher incidence of winter injury. The diseases
cause the production of dry, seedy berries and the stunting and prevention of
new cane formation. Weakened canes are broken easily by the wind and are more
susceptible to winter injury. The plants might show water stress and nutrient
deficiency symptoms since the movement of water and nutrients throughout the
plant is disrupted. With cane gall, black and purple raspberries are more often
infected than red raspberries and blackberries.

Disease CycleBoth diseases are caused by soilborne
bacteria (crown gall: Agrobacterium tumifaciens and cane gall: Agrobacterium
rubi) that infect the plant only through wounds. Wounds can result from natural
causes (e.g., insect feeding, frost damage) or from mechanical causes (e.g.,
pruning, cultivating, harvesting). The bacteria overwinter in the soil and in
galls. Bacteria are then spread by splashing rain, running water, cultivation,
and pruning from soil and infected plants. As the galls enlarge, the soil can
become heavily infested and will remain so for many years.

Disease Management The best control
measure is prevention. Plant only certified, disease-free nursery stock, and
take care not to wound the plants, especially the root systems, at planting
time. Try to plant only in sites with no history of the diseases, or wait at
least 3 to 5 years before replanting in the site. If a diseased plant is
detected, remove and burn the roots and tops of the plant. Dispose of the soil
surrounding the roots of the affected plant. Titan seems to be especially
susceptible to crown gall, as do some of its relatives. No chemical control is
known.